Batch sorption and fixed-bed elution for Pd recovery using stable amine-functionalized melamine sponge

Sorption-based techniques have been widely studied for metal recovery. Conventionally, sorption and desorption steps are operated in fixed-bed column system under one-pass mode (FO); however, such requires a large volume of solution passing the bed when feed concentration is low. In this study, highly stable amine-coated alginate melamine (ML/APG) sponge was prepared applied combined process involving recirculation (FR, simulating batch system) FO Pd(II) concentration. The efficiency evaluated terms both recovery utilization sponge. Results show that ML/APG 3 M nitric acid, sodium hydroxide chloride after shaking at 300 rpm 72 h with mass loss less than 0.9%. maximum capacity obtained by Langmuir model increases from 9.7 mg g?1 to 134.3 amine functionalization. equilibrium could be achieved amount time using FR compared FO. For example, it only needs 0.7 L 20 L?1 achieve FR, while required 1.8 flow rate 1 mL min?1 more 5 10 This means improved rational use sorbent thus increased efficiency. elution step, 40 completely desorb exhausted sponge, needed 200 FR. allows effective elution. reusability low-concentration were combining step step. maintains 96% 100 min reaction during cycles. performance 100% 50 acidic thiourea solution. factor (CF, ratio eluate over its used sorption), above or close 70 first mL-sample much second mL-sample.